In the field of ink jet printers and especially in the matter of multiple-nozzle print heads, there has been a problem in maintaining the ink conduits or passageways in precise position and of keeping such conduits or passageways sealed or separated from each other in the areas of intake of the ink and of the nozzle portion of the print head. The difficulty of sealing the conduits from each other in the vicinity of the nozzles is apparent from the close proximity of the nozzles which allows or provides only a very small sealing area.
One method of making an ink jet print head has included a plastic casting wherein the resin or like material is cast at room temperature and under sufficiently high pressure to attempt to minimize the presence of air bubbles which may cause pockets or uneven surfaces for passage of the ink fluid.
Another method has included the use of elevated heat temperatures and pressures in the plastic molding, however, it has been found difficult to maintain precise position of the parts in the mold itself.
Prior art which is representative of the production of ink jet print heads includes British Pat. No. 1,355,915 and German Specification No. 2,164,614, which disclose that it is possible to replace the drive elements in the print head, but with no indication in the disclosure as to how the print heads can be produced in a simple and economic manner.
German Specification No. 2,532,037 discloses a multiple nozzle ink jet print head produced through use of ceramic plates with etching of the necessary cavities and channels therein. Such type of print head production however appears to be very complicated and involve high costs, so that the disclosed method would ordinarily be unsuitable for mass production.
German Specification No. 2,543,451 corresponding to U.S. Pat. No. 4,158,847 shows a piezoelectrically operated print head for ink printing devices which is made of plastic in a casting procedure. Protective tubes which serve as inner electrodes are inserted into ceramic tubes which serve as drive elements for the print head and metal rods are then inserted into the tubes which extend from a fluid supply cavity to the ejection nozzles. When the plastic casting has hardened, the metal rods are removed and the tubes act as channels or conduits for the ink. This structure has the disadvantage that at least a portion of the drive element is not accessible and cannot be replaced if found defective.